This invention relates to an electrical speed sensor having a pair of relatively confrontingly rotatable pole members, one being fixed to the transmission housing of a vehicle and the other being connected for rotation to a shaft driven by an output shaft of the transmission.
In order to increase the efficiency of the sensor, it is required to reduce the air gap between the pole members to a minimum. For meeting such requirement it has been the practice in the art to calculate the air gap in design within very small range, such as for example, of from 0.1 to 0.2 mm. It has been found that any deflection or rattle of one of the members, such as a rotor, relative to the other member, such as a stator, causes a considerable rate of variation of the electric output of the sensor whatever small amount the deflection may be. The variation of the electric output results into an unavailable output for being employed as a signal indicating the rotational speed of the vehicle wheel for the purpose of any controlling system of the vehicle.
In order to prevent the deflection or rattle of the rotor, it has been tried to flexibly or pivotally couple a driving shaft of the sensor with the rotor, so that any deflection or rattle of the driving shaft is provented from being transmitted to the rotor, by such coupling.
The use of this coupling entails increase of associating parts and an extra complicated handling of the parts themselves when the sensor is being assembled with added inconvenience and expense to the user.